This invention relates to circular knitting needles utilized for various yarns.
It is known in the art, that in the connection between the needle tips and the ends of a flexible intermediate portion of the needle pressing deformations can occur in the ends of the intermediate portion inserted into a recess formed at an end of each tip. Knot-like thickened portions are provided on the end surfaces of the tips which cause tension stresses in the assembly. Polyamide of very high transverse contraction capabilities, a modulus of elasticity which is smaller by 10,000 to 1,000,000 times as compared to steel and with a perfect volumetric stability, has been utilized. However, when the ends of the intermediate portion are clamped within the recess by filling the free volume between the walls of the recess and the end of the flexible portion, the ends of the intermediate portion become elongated along the recess and the initial connection of the knot-like thickened portions with the end surfaces of the tips becomes loosened. The bending stresses can occur in the area of the clamping contact which may cause a strong twisting within the assembly. In the assembly a gap or clearance normally occurs between the knot-like thickened portions and the end surface of the tips in which yarn to be used may be torn.
In order to prevent extension of the polyamide filament from the recess during the assembling it has been suggested to provide the knot-like thickened portions with further thickened elements at the ends thereof. This permitted to form radial pressure forces between said knot-like thickening portions and the ends of the intermediate portion to be inserted into the recess thereby freeing the recess in the direction of its ground. This tends in connection with the inner smooth recesses, that the radial reduction in the ends of the tips and therewith produced deformation of the thickened portions, to produce tension forces in the region of knot-like thickened portions, which during the clamping process remain in the arrangement. They should guarantee that knot-like thickened portions have higher tension stresses at their end surfaces so that in the area of clamping action bending stresses may occur which may prevent construction of the gaps.
The above-described method of manufacturing circular knitting needles in general was reliable, however it may cause discomfort when a diameter of the end of the intermediate portion of the knitting needles surrounded by polyamide filaments has more or less strong allowances within permissible tolerances. It has been particularly observed in such cases that needle tips assembled with the ends of the intermediate portion and having galvanized outer surfaces may be damaged during the forging treatment. Except the problem caused by the defects in tolerances, the needle points in the area adjacent to knot-like thickened portions can overlap the corresponding round outer edges of the outer surfaces of the ends during the forging operation. This can cause catching if the woolen threads are used for knitting.